On Sunday, December 27, 2015 at 11:07:23 AM UTC-5, Cursitor Doom wrote:
Hi all,

I have an elderly Casio scientific calculator (fx-3400p) which I've owned
since new in 1991 (so I'm quite attached to it). Lately, the numeral '2'
key has become a bit flaky inasmuch as every press doesn't always
register 100% of the time any more. I know these things are dirt cheap to
replace, but I've got used to the layout of it and don't really want to
upgrade to something new if it can be fixed reasonably easily.
Any ideas what the problem might be?
thanks.

Try cleaning the rubber bubble carbon and PC board with alcohol and cue tip.. Works for remote controls most of the time. Failing this buy the remote control rebuild kits , around 20 bucks , that will resurface the carbon on the rubber bubble. Good luck with it and I suspect you will be okay with the easy fix of alcohol and a cue tip.